Just last week I was able to run 5 miles. I could have run 10 miles if I wanted to. Today when I ran it was so difficult. I was breathing hard. I wasn't running as fast. I just felt heavy. I could barely run two miles. I refuse to believe that two bottles of beer can make that much difference. That, to me, just doesn't make sense logically. Can anyone help me out here?? Is it because I was running at a different time than when I normally run?

you hit the proverbial wall dude, your body can still do more but your mental state is holding you back. take a day or two off and that should allow your body and more importantly your mind enough time to rebuild and regroup..........Rockin'

The simple answer is your mental state. I can sometimes run for 10 miles and not even be breathing heavy, the next day after a mile im gone. The most important part of any excercise is mental. Maybe something has distracted you or affected you quite badly?

Just last week I was able to run 5 miles. I could have run 10 miles if I wanted to. Today when I ran it was so difficult. I was breathing hard. I wasn't running as fast. I just felt heavy. I could barely run two miles. I refuse to believe that two bottles of beer can make that much difference. That, to me, just doesn't make sense logically. Can anyone help me out here?? Is it because I was running at a different time than when I normally run?

Sounds like you're overtrained, under-nourished, or have a cold/flu coming. If it's a one off, don't worry too much about it.

Good idea to get a heart monitor to use for your runs as well. You can pick them up pretty cheap. Sometimes your body genuinely is really struggling with the work, sometimes it can be in your head.

mind over matter. Everyone hits that. Now you saying you refuse to believe a beer can do that so in a way you blaming the beer mentally and allowing yourself to quit. Also your body do need rest and needs to be well hydrated for prolonged runs.